U.S. Pat. No. 3,180,872 (Cochran et al.) generically discloses 2- and 4-(1-halovinyl)pyridines, their acid addition salts, and their utility as nematocides, as well as specifically teaching various 2-vinylpyridine derivatives and one 4-vinylpyridine derivative--4-(1-chlorovinyl)pyridine hydrochloride.
According to column 4, lines 41-55, such compounds can be prepared by converting 2- or 4-vinylpyridine to the appropriate 2- or 4-(1,2-dihaloethyl)pyridine and refluxing that product in anhydrous ethanol. This process appears to have been successfully employed in the preparation of 2-vinylpyridine derivatives but has been found to be unsatisfactory in the preparation of 4-(1-chlorovinyl)pyridine derivatives because of the reactivity of ethanol toward 4-(1,2-dichloroethyl)pyridine. For example, an attempt at preparing 4-(1-chlorovinyl)pyridine by refluxing 4-(1,2-dichloroethyl)pyridine hydrochloride in ethanol led to the formation of 4-(1-chloro-2-ethoxyethyl)pyridine hydrochloride.
It would be desirable to find a simple and clean method of preparing 4- (1-chlorovinyl)pyridine and salts thereof from 4-(1,2-dichloroethyl)pyridine.